TECHNICAL FIELD

The invention relates to a method for disassembling rivets on textile articles.

PRIOR ART

The textile industry is one of the most polluting industries worldwide (after the petrochemical industry) and requires an extremely high water and chemical consumption at the different stages of the production process. Worldwide textile consumption was estimated at 95.6 million tons in 2015. Textile consumption is expected to increase further to around 8.5 trillion tons by 2030. It goes without saying that this growing demand for fashion textiles is exerting great pressure on the limited material and energy resources present on Earth. Today, one full truck of textile is discarded every second. Only 1% of the materials used in the textile industry are recycled materials. However, the focus is increasingly shifting to the circular economy, within which there are many opportunities for the textile industry.

In the textile industry, metal rivets originally performed a fastening and/or reinforcement function, mainly with seams subject to wear. Nowadays rivets are used much more widely in the textile industry, for example as a press-stud, as a lace hole or eyelet, as a connecting means or purely as a decorative detail. Rivets are appreciated, mainly because of their low cost, good strength properties, and their simple manner of application.

Most textile-based products that are composed of several components, and which may have rivets, are very difficult to recycle and/or reuse at the end of their life. If these are nevertheless recycled, an attempt is made to separate the different materials that make up the product. To this end, the textile products are shredded, after which they are possibly sorted by material type under the influence of air pressure, magnetism and/or centrifugation. In this way, among other things, hard materials and/or points are removed from the textile. However, this process is energy intensive and complex, and results in reduced quality and/or economic value of the recycled material. The presence of rivets in these composite textile products is often a very difficult factor in this recycling process and ensures a reduced purity of the recycled materials. Due to the reduction in quality and purity inherent in the recycling process, recycled textile products are often only suitable for so-called 'down-cycling'. The materials are reused, but they are only used in a significantly different market, for example as filler material in insulation mats and concrete.

Accordingly, there is a need for an efficient process for separating and/or disassembling the individual components of textile articles which include rivets, eliminating shredding, and ensuring the quality and purity of the recycled materials. Reuse of both the rivets and the individual textile components should be simplified here.

EP2861793 describes a sewing method with built-in disassembly function of textile articles. In this method, stitching made from a thread incorporating metal particles will come apart under the influence of electromagnetic waves. However, the presence of rivets in a textile product is still a complicating factor in reuse and recycling thereof. Textile products comprising rivets must of necessity be shredded in order to remove the rivets.

Disassemblable alternatives to the currently known rivet are currently very scarce. JP3140636U describes a disassemblable alternative, which, however, is very time- consuming to assemble via a screw mechanism. This mechanism inherently allows for only a limited number of embodiments, where a screw is located centrally through the textile, and where the decorative head of the rivet is specifically designed to allow rotation. The rivet as described in JP'636 is therefore not suitable for press studs, eyelets, or decorative buttons, among others. Moreover, disassembling the rivets requires a lot of manual labour, with each rivet having to be unscrewed separately.

The object of the present invention is to at least solve some of the above-mentioned problems or disadvantages.

SUMMARY OF THE INVENTION

To this end, the invention provides a method according to claim 1. In a first aspect, the invention relates to a method for disassembling rivets on textile articles, which rivets comprise at least two separate rivet elements, at least one of said rivet elements being made at least in part from a memory material having at least a first memory transfer temperature. The rivets are disassembled by heating them. The present method allows the rivets, and in particular the rivet element comprising the memory material, to spontaneously deform under the influence of a changing temperature, which enables the various rivet elements to be easily disconnected.

Preferred embodiments of the method are described in dependent claims 2 to 10.

The impact of the textile industry on the environment cannot be underestimated. The textile industry is one of the most polluting industries in the world. The present invention provides a method by which this can be addressed. Thanks to this invention, the amount of textile articles that are discarded, not recycled or reused can be drastically reduced.

The built-in disassembly function eliminates shredding for recycling so that the size of the recycled materials is not further reduced and the mechanical properties of the recycled material are better preserved. In addition, the method according to the present invention enables multi-component textile articles to be easily disassembled at the end of their useful or expected life. This prevents possible contamination of the recycled materials caused by not or poorly disassembling the various parts. Since the decrease in the quality of recycled materials from the textile industry is mainly caused by a decrease in the mechanical properties of the material as well as a reduced degree of purity, the present invention enables a person skilled in the art to indeed obtain high quality recycled products from the textile industry.

The disassembly and reuse of high-quality materials results on the one hand in enormous financial savings in the processing of textile waste and on the other hand, raw materials are also obtained for the production of new textile articles, so that the financial savings also continue in the production of new textile articles. Since much more textile is already being produced today than the material and energy sources on earth allow in principle, the circular reuse of textile products has the advantage that more leeway is created on the market, so that availability and pricing are not put under pressure. Thanks to the possibility of having the disassembly process run semi- automatically or fully automatically, this is, in contrast to the existing processes for recycling textile articles, a low-labour process and therefore also a relatively cheap process.

In a second aspect, the present invention provides a rivet according to claim 11. The rivet comprises at least two separate rivet elements, at least one of said rivet elements being at least partly made of a memory material having at least a first memory transfer temperature. The rivet according to the present invention can change from at least one temporary form to a permanent form and vice versa under the influence of external stimuli, allowing for a smooth disassembly.

Preferred embodiments of the rivet are described in dependent claims 12 to 16.

A final aspect concerns a textile article according to claim 17. The textile article comprises rivets, which rivets comprise at least two separate rivet elements, at least one of said rivet elements being made at least in part from a memory material. The memory material here has at least a first memory transfer temperature, at which said rivets can be easily disassembled by heating them up. This the simple disassembly of rivets on the textile article[.viBi], whereby a large quantity of textile articles can be processed simultaneously. This eliminates the need for manual removal of rivets and the disassembly process can be automated in its entirety.

Preferred embodiments of the textile article are described in dependent claims 18 to 20.

The materials obtained by the invention after disassembling the rivets can be used as raw materials for the production of new textile articles, thanks to the retention of their mechanical properties and their high degree of purity. The rivets themselves can also be reused in a simple way. In this way, the present invention not only helps to reduce the total amount of waste generated by the textile industry and the associated pressure on the ecosystem, but also to reduce the energy and water consumption associated with the production of new, unused textile materials.

DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic cross-section of a rivet according to an embodiment of the present invention in open and closed form.

Figure 2A shows a perspective view of a rivet, in particular a button with open and closed button face, according to an embodiment of the present invention.

Figure 2B shows different decorative embodiments of a button face.

Figure 3 shows a perspective view of a rivet, in particular of the various rivet elements of a press stud, according to an embodiment of the present invention. Figure 4 shows a perspective view of a rivet, in particular of the various rivet elements of a ring opening or 'eyelet', according to an embodiment of the present invention.

Figure 5 shows a possible embodiment of a heating unit for disassembling rivets.

Figure 6 shows, respectively, the temperature profile, the deformation, and the tension on a rivet according to an embodiment of the present invention when it is assembled and disassembled several times.

DETAILED DESCRIPTION

The invention relates to a rivet and a method for disassembling rivets on textile articles.

Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as commonly understood by a person skilled in the art to which the invention pertains. For a better understanding of the description of the invention, the following terms are explained explicitly.

In this document, 'a' and 'the' refer to both the singular and the plural, unless the context presupposes otherwise. For example, 'a segment' means one or more segments.

When the term 'around' or 'about' is used in this document with a measurable quantity, a parameter, a duration or moment, and the like, then variations are meant of approx. 20% or less, preferably approx. 10% or less, more preferably approx. 5% or less, even more preferably approx. 1% or less, and even more preferably approx. 0.1% or less than and of the quoted value, insofar as such variations are applicable in the described invention. However, it must be understood that the value of a quantity used where the term 'about' or 'around' is used, is itself specifically disclosed.

The terms 'comprise', 'comprising', 'consist of', 'consisting of', 'provided with', 'include', 'including', 'contain', 'containing', are synonyms and are inclusive or open terms that indicate the presence of what follows, and which do not exclude or prevent the presence of other components, characteristics, elements, members, steps, as known from or disclosed in the prior art.

Quoting numerical intervals by endpoints comprises all integers, fractions and/or real numbers between the endpoints, these endpoints included. In a first aspect, the present invention relates to a method for disassembling rivets on textile articles, which rivets comprise at least two separate rivet elements, and wherein at least one of said rivet elements is at least partially made of a memory material having at least a first memory transfer temperature.

The term 'textile' or 'textile product' denotes a deformable product resulting from the spinning, and optionally twisting, of fibres and/or filaments into yarn, which are then processed into a multi-dimensional product by weaving, crocheting, knitting, knotting, braiding, felting, or other fabric techniques.

The term 'textile article' or 'textile-based article' is used in the context of the present invention to denote articles which are at least in part textile and/or leather. Non-limiting examples of textile articles are clothing and footwear; safety clothing including gloves against cuts; household textile articles such as cleaning cloths, mops, sheets, blankets, tea towels, towels, tablecloths, handkerchiefs, mattresses and bed linen; home textiles including net curtains, curtains, carpet, floor covering, furniture coverings and sun screens; technical textile articles such as tarpaulins, tents, parachutes, screens, ropes; geotextiles such as dike protection, erosion protection, reinforcement of the subsoil under roads; rubber reinforcement such as in bicycle and car tyres, conveyor belts, hoses, rubber boats and textile articles for vehicles such as cars, trains and aircraft, including airbags, seat covers and seat belts. The object of the present invention aims to emphasise the recycling and/or reuse of clothing and/or footwear.

The term 'rivet' refers to a fastener that consists of at least two separate rivet elements. Generally, one of these elements is a rivet consisting of a pin or rod that has two ends. The first end consists of a bulge, the 'swage head', and the second end consists of a pin. When attaching a rivet, the pin is pushed through a hole in one or more rivet elements, after which the pin is deformed into a second, thickened end, the 'closing head', which ensures a permanent coupling of the various rivet elements. Within the context of the present invention, the term 'rivet' refers to both a functional fastener and an ornamental and/or decorative fastener.

The pin of a rivet according to the present invention exists in at least two forms. In the rest state, before assembly, the pin of the rivet is in the stretched state. When the rivet is in the assembled state, the pin is deformed into a closing head so that the rivet cannot be removed. When disassembling the rivet, the closing head must be removed. This can be done in a non-destructive way by bringing the pin (back) to a stretched state, so that the rivet can be easily removed from the textile article. These shapes are remembered according to the present invention by the memory material contained in at least one of the rivet elements.

According to some embodiments, the rivet element comprising the memory material is shaped like a rivet. According to an embodiment, said rivet element is formed as a ring. Equivalent to the rivet, the ring comprises one or more protrusions and/or edges subject to deformation in order to obtain a coupling between the different rivet elements. According to some embodiments, the rivet element comprising the memory material has a form other than a rivet or a ring.

A 'memory material', 'memory polymer' or 'shape memory polymer' is used in the context of the present invention to refer to smart materials comprising one or more polymers. These materials can return from a deformed or temporary form to their original or permanent form under the influence of one or more external stimuli. The transition from such a temporary form to a permanent form is referred to below as a 'memory effect'. Memory materials may be able to transition between multiple temporary shapes, having a dual, triple, or multiple memory effect. In the context of the present invention, each of these forms is associated with one or more 'memory transfer temperatures', i.e., the temperatures at which deformation is triggered into a particular temporary or permanent form of the memory material.

Memory materials useful in the context of the present invention include, but are not limited to, memory metals and memory polymers, including electroactive polymers, in which volumetric changes occur under the influence of voltage or a change in electric field; magnetic memory materials, wherein form changes occur in response to a change in magnetic field; magnetostrictive materials wherein form changes occur under the influence of a magnetic field, or change of magnetisation due to mechanical stress; chemo-responsive materials that change form and/or volumetrically as a result of an external chemical or biological component; and thermo-responsive polymers that undergo form and/or volumetric changes under the influence of temperature.

The present method allows the rivet, and in particular the rivet element comprising the memory material, to spontaneously deform under the influence of an external factor, stimulus and/or impetus. Depending on the chosen material, such external factor, stimulus and/or impetus comprises a changing voltage, a changing electric field, a changing magnetic field, a changing magnetisation, a changing presence or absence and/or a changing concentration of a chemical or biological component, a changing temperature, or combinations thereof. According to some embodiments, said external factor, stimulus and/or impetus comprises a changing electric field, a changed magnetic field or a changing temperature.

According to a further or alternative embodiment, the present method allows the rivet, and in particular the rivet element comprising the memory material, to deform spontaneously under the influence of a changing temperature, which enables the smooth disconnection of the various rivet elements. As a result, the shredding of textile articles for recycling is superfluous, and the various textile components can be reused unreduced and with retention of mechanical properties. Moreover, since most textile products are produced from different materials, the present process allows the different materials to be recovered with high purity and in a non-destructive manner. The rivets themselves can also easily be reused multiple times in the production of new textile articles.

The disassembly and reuse of high-quality textile materials, as well as rivets on these textile materials, while retaining quality and purity, results in enormous financial savings in the processing of textile waste and the production of new textile articles. The method provides a disassembly process that can take place semi-automatically or fully automatically, which makes the recycling of textile articles cheaper and more efficient than the recycling processes as known from the prior art.

In addition, the recycling materials obtained thanks to the invention can be used after disassembling the rivets as raw materials for the production of new textile articles. Thus, according to one embodiment, the rivets of the present invention can be fully or partially reused after disassembly. In this way, the present invention contributes not only to reducing the total amount of waste generated by the textile industry and the associated pressure on the ecosystem, but also to reduce the energy and water consumption associated with the production of new textile articles.

According to some embodiments, the deformable rivet element is made entirely of the memory material.

Preferably, the memory material comprises at least a first and a second memory transfer temperature. Multiple memory temperatures allow the memory material to take on multiple temporary shapes under the influence of a changing temperature. In particular, it is possible, for example, to attach rivets without exerting a mechanical force and merely under the influence of temperature. More preferably, the memory material comprises at least a first, second and third memory transfer temperature.

According to a further or alternative embodiment, the rivets are attached to the textile article by mechanical deformation, and a loose rivet element comprising the memory material is heated to a temperature within the range of the first memory transfer temperature before and/or during the mechanical deformation. The application of the rivet within this temperature range allows the fixation of the rivet to the textile article in its temporary, closed form. The 'closed form' of the rivet is understood to mean the temporary form, in which all parts of the rivet are firmly coupled to each other and the textile parts adequately connect with each other. After the rivet has been applied to the textile article, the closed form is retained, also outside the stated temperature range. The coupling of the different rivet elements therefore remains intact at room temperature, when a person is wearing a textile article, as well as during washing, ironing and other frequent use situations.

The term 'range', specifically the range of a memory transfer temperature, refers to a range that is around the discrete value of the memory transfer temperature. Preferably, this range does not exceed 5°C on either side of this discrete value. For example, when a memory transfer temperature of 100°C is indicated, its range is preferably between 95 and 105°C. More preferably, the range does not exceed 3°C either side of the discrete value, even more preferably no more than 1°C. A narrow range allows precise adjustment of the different temporary shapes of the memory material.

According to a further or alternative embodiment of the method, the disassembling of the rivets takes place by heating the rivets to a temperature within the range of the first memory transfer temperature. The first memory transfer temperature according to this embodiment is the temperature at which the memory material spontaneously returns to its permanent, open form. The 'open form' of the rivet is understood to be the permanent form in which the different rivet elements are not permanently connected to each other. They consequently come apart spontaneously. This has the advantage that both the rivet and the individual components of the textile article, which may be held together by the rivets, can be reused undamaged.

According to an embodiment, upon application of mechanical deformation and heating, the rivet is 'programmed' into its temporary, closed form. When heated and in the absence of mechanical deformation, the rivet returns to its permanent, open form. Preferably, heating of the rivet comprises a two-stage heating process upon disassembly. A two-stage heating process allows, especially if the memory material has multiple memory transfer temperatures, a specific sequence of programmed shapes, wherein the number of mechanical and/or physical operations required can be further reduced.

According to an embodiment, the first memory transfer temperature is comprised between 100 and 200°C. A high memory transfer temperature is desirable as the rivet must remain permanently coupled in use situations such as wearing the textile article as well as washing and/or ironing the textile article. A lower memory transfer temperature poses a significant risk of disconnecting of the rivets. Preferably, the first memory transfer temperature is comprised between 100 and 160°C. More preferably, the first memory transfer temperature is comprised between 100 and 140°C.

According to some embodiments, the difference between the first memory transfer temperature and the second memory transfer temperature is greater than 50°C, preferably greater than 60°C, more preferably greater than 70°C. Memory materials that are able to take on more than one temporary form benefit from a greater difference between the different memory temperatures in order to unambiguously distinguish between the different discrete temporary shapes.

According to a further or alternative embodiment, the two-stage heating process comprises sequentially heating the rivet element to a temperature comprised between 100 and 140°C and then to a temperature comprised between 100 and 200°C. Preferably, the rivet is heated sequentially between 100 and 120°C and then between 140 and 200°C, more preferably sequentially between 110 and 130°C and then between 160 and 180°C.

Heating may take place both directly and indirectly. Apparatus and/or equipment suitable for achieving the desired temperature are known to those skilled in the art and include, for example, heating devices based on an electrical resistance or devices that use infrared radiation. Indirect heating can be done, for example, by placing the textile article in an oven.

According to a further embodiment, the disassembling of the rivets takes place automatically or semi-automatically. Preferably, the rivets and/or textile articles are shaken or moved during heating. The movement automatically separates rivet elements from each other once the rivets return to their open, permanent form. Preferably, a suitable device, such as an oven, optionally comprises a rotating drum to further separate the parts of the textile article from each other. Automation of the process reduces the costs of the disassembly process as little or no manual labour is involved.

According to a further or alternative embodiment, disassembly takes place in a device comprising a heating unit, provided with heating elements and optionally one or more steam generators. The device may be provided with a rotating drum. Disassembly in such a unit allows simultaneous disassembly of a large number of rivets on different textile articles. The disassembly process may be semi-continuous to continuous.

According to an embodiment, the rivets are removed from the textile article after disassembling the rivets. Rivet as well as various other parts of the textile article can be directly reused as raw material in the production of recycled and/or new textile articles.

The present invention further provides a method of attaching rivets with an automatic or semi-automatic disassembly function to a textile article, wherein the rivets are attached by mechanical deformation. The method is characterised in that the rivets comprise at least two separate rivet elements, at least one rivet element of which is manufactured at least partially from a memory material. The memory material has at least a first memory transfer temperature. Before and/or during the mechanical deformation, said rivet element is heated to a temperature within the range of the first memory transfer temperature. The application of the rivet within this temperature range allows the fixation of the rivet to the textile article in its temporary, closed form. After the rivet has been applied to the textile article, the closed form is retained, also outside the stated temperature range. The coupling of the different rivet elements therefore remains intact at room temperature, when a person is wearing a textile article, as well as during washing, ironing and other frequent use situations.

According to an embodiment, the first memory transfer temperature is comprised between 100 and 200°C. A high memory transfer temperature is desirable as the rivet must remain permanently coupled in use situations such as wearing the textile article as well as washing and/or ironing the textile article. A lower memory transfer temperature poses a significant risk of disconnecting of the rivets. Preferably, the first memory transfer temperature is comprised between 100 and 160°C. More preferably, the first memory transfer temperature is comprised between 100 and 140°C. According to some embodiments, the difference between the first memory transfer temperature and the second memory transfer temperature is greater than 50°C, preferably greater than 60°C, more preferably greater than 70°C. Memory materials that are able to take on more than one temporary form benefit from a greater difference between the different memory temperatures in order to unambiguously distinguish between the different discrete temporary shapes.

According to a further or alternative embodiment, the two-stage heating process comprises sequentially heating the rivet element to a temperature comprised between 100 and 140°C and then to a temperature comprised between 100 and 200°C. Preferably, the rivet is heated sequentially between 100 and 120°C and then between 140 and 200°C, more preferably sequentially between 110 and 130°C and then between 160 and 180°C.

According to an embodiment, the mechanical deformation is obtained by means of one or more operations for attaching rivets as known from the prior art. To this end, riveting pliers or another device suitable for applying rivets can be used.

According to a further or alternative embodiment, the rivets are attached by heating said rivet element before and/or during the mechanical deformation, said mechanical deformation exerting a force comprised between 250 and 1500 N on the rivet element. This force is preferably comprised between 300 and 1000 N, more preferably between 300 and 800 N.

According to some embodiments, the rivets are heated before the mechanical deformation is applied. Rivets can be placed in a heating device, such as an oven, for this purpose. According to some embodiments, the rivets are heated during the application of the mechanical deformation. Riveting pliers or a riveting device may be used for this purpose, in which one or more heating elements are arranged. The rivets may be heated both before and during carrying out the mechanical deformation. Under the influence of the heating and mechanical deformation, the rivets are fixed in their closed, temporary form. Fixation of the closed, temporary form is retained, even after cooling and removal of the mechanical deformation.

A second aspect of the present invention relates to a rivet with built-in disassembly function, the rivet comprising at least two separate rivet elements, at least one of said rivet elements being made at least in part from a memory material having at least a first memory transfer temperature. The rivet according to the present invention can transition from at least one temporary form to a permanent form and vice versa under the influence of external stimuli.

According to some embodiments, the deformable rivet element is made entirely of the memory material.

Preferably, the memory material has at least a first and a second memory transfer temperature. Multiple memory temperatures allow the memory material to take on multiple temporary shapes under the influence of a changing temperature.

According to a further or alternative embodiment, the rivet memory material comprises one or more polymers. Suitable memory polymers comprise thermoplastics, thermosets, interpenetrating networks, semi-interpenetrating networks, and mixed networks of polymers. The term 'semi-interpenetrating network' denotes a structure in which a cross-linked polymer is interwoven with another polymer. The term 'interpenetrating network' denotes a structure in which a cross-linked polymer is interwoven with two other polymers. Said polymers can be a single polymer or a mixture of two or more polymers. The polymers can be linear or branched thermoplastic elastomers with side chains or dendritic structural elements. Suitable polymer components for forming a shape memory polymer comprise, but are not limited to, polyphosphazenes, polyvinyl alcohols, polyamides, polyester amides, polyamino acids, polyanhydrides, polycarbonates, polyacrylates, polyalkylenes, polyacrylamides, polyalkylene glycols, polyalkylene oxides, polyalkylene terephthalates, polyorthoesters, polyvinyl ethers, polyvinyl esters polyvinyl halides, polyesters, polylactides, polyglycolides, polysiloxanes, polyurethanes, polyethers, polyether amides, polyether esters, polystyrene, polypropylene, polyvinyl phenol, polyvinylpyrrolidone, chlorinated polybutylene, poly-octadecyl vinyl ether, ethylene-vinyl-acetate, polyethylene, polyoxymethylene, polyethylene oxide, polyethylene terephthalate, polyethylene/nylon graft copolymer, polycaprolactone/polyamide block copolymer, poly-caprolactone dimethacrylate n-butyl acrylate, poly (norbornyl-polyhedral oligomeric silsesquioxane), polyvinyl chloride, urethane / butadiene copolymers, polyurethane block copolymers, styrene-butadiene-styrene block copolymers, copolymers of any of the foregoing polymers, or combinations thereof.

Memory polymers are extremely suitable for use in the rivet according to the present invention since these materials are inexpensive and can be easily processed in various shapes and colours, allowing for a far-reaching personalisation of rivets, and textile articles comprising the rivets.

The term 'thermoplastic polymer' refers to a polymeric material that becomes deformable under the influence of heat and hardens on cooling. The term 'polymer' is used to denote an organic compound whose molecules consist of a sequence of identical or similar parts, the monomers, that are chemically linked together.

The said polymers are preferably selected from the group of polyethylene, polypropylene, polyamide, polyester, polyether, polylactide, polyurethane, polyoxymethylene, copolymers of the foregoing polymers, or combinations thereof. According to the present invention, polymers can be selected depending on the intended memory transfer temperature, as well as depending on other material properties, such as hardness, melting temperature, biodegradability, etc.

According to an embodiment of the rivet, said memory material is a mixture of polyethylene and polypropylene. This mixture has the advantage that it can take three forms, i.e. two temporary forms and one permanent form.

Preferably, the ratio between polyethylene and polypropylene in the memory material is comprised between 2:8 and 8:2. With this polyethylene / polypropylene ratio in the memory material, an optimal balance is obtained between hardness and strength of the rivet in the closed, permanent form, and deformability as well as form recovery of the rivet under the influence of the changing stimuli, in particular temperature, on the other hand. These properties contribute to the strength and therefore the quality of the rivet, as well as to good disassembleability. More preferably, the ratio of polyethylene to polypropylene in the memory material is comprised between 6:4 and 4:6. Most preferably this ratio is 5:5. The transition between the permanent and the temporary forms of the memory polymer is extremely efficient at this ratio and can be repeated almost indefinitely, permitting frequent reuse of the rivets according to the present invention.

According to a further or alternative embodiment, said memory material is a cross- linked material. The term 'cross-linking' in the context of the present invention refers to the formation of covalent bonds between the units of the same polymer chain or between units of different polymer chains. These covalent bonds determine the permanent form of the memory polymer and can be introduced, on the one hand during the polymerisation process, and on the other after polymerisation. Cross-linking of the polymer units contributes to the strength and elasticity of the material, as well as the development of materials with memory effects suitable in light of the present invention. For example, by cross-linking two polymer chains consisting of different units, it is possible to develop materials with new chemical and/or physical properties, including altered memory effects, which occur under altered external stimuli. In this way, cross- linking makes it possible to adapt the properties of the memory material to the specific function of the rivet. In this case, the cross-linking gives the materials rubber-like properties. After cross-linking, the resulting material is characterised as a thermoset rather than a thermoplastic.

Cross-linking according to the present invention takes place by physical cross-linking and/or chemical cross-linking. Chemical cross-linking can be carried out by adding a cross-linking agent or oxidising substances, such as radicals, or by using electromagnetic radiation. According to a further embodiment, the polymers for use in the memory polymer are subjected to oxidative cross-linking using one or more peroxides as an initiator to speed up cross-linking.

According to a further embodiment of the present invention, the initiator is selected from the group of peroxides including benzoyl peroxide, dicumyl peroxide (DCP), di- tert-butyl peroxide, 2,5-dimethyl-2,5-di (tert-butyl peroxy)-hexane (DHBP), l,l-di-(t- butylperoxy)-3,5,5-trimethylcyclohexane (TMCH), dicumyl peroxide divinylbenzene (DCP-DVB), or combinations thereof.

Preferably, cross-linking is initiated by 2,5-dimethyl-2,5-di (tert-butyl peroxy)-hexane (DHBP), dicumyl peroxide divinylbenzene (DCP-DVB), or a combination thereof. DHBP is liquid at room temperature and is well absorbed by the polymer mixture. In addition, DHBP exhibits very high cross-linking efficiency at high temperature (150°C to 200°C). According to a further or alternative embodiment, DHBP is administered to the polymer mixture on a carrier, preferably the carrier is propylene. Cross-linking is preferably carried out at a temperature comprised between 160 ° C and 180 ° C. Cross-linking takes place in some embodiments for 1 to 300 minutes, preferably between 20 and 240 minutes, more preferably between 60 and 120 minutes.

According to a further or alternative embodiment, the memory polymer comprises a chemically cross-linked PE/PP blend. Cross-linking of these polymers results in a synergistic improvement in the mechanical properties of the memory polymer. Moreover, PE and PP are extremely cheap and readily available.

Most preferably, cross-linking is initiated by 2,5-dimethyl-2,5-di (tert-butylperoxy)- hexane (DHBP). The different memory transfer temperatures of the cross-linked PE/PP blend by means of DHBP are optimal in view of the intended application field of rivets according to the present invention. Production and disassembly of textile articles takes place at a temperature which is sufficiently low so that the various textile components of the article are not damaged. The disassembly temperature is also significantly higher than current usage temperatures, such as when wearing, washing and/or ironing the textile articles.

According to an embodiment, the DHBP is present in the memory polymer or memory polymer blend at a concentration comprised between 1.0 and 10.0 m%. Within this range, optimal cross-linking between PE and PP is obtained, whereby a stable memory material is obtained that can switch frequently between its different forms without loss of quality. Preferably, the DHBP is present at a concentration of between 4.0 and 8.0%, more preferably between 5.0 and 7.0%. Most preferably, about 6.0 m% BHBP is present in the memory polymer or memory polymer blend.

A third aspect of the present invention relates to a textile article provided with rivets, wherein the rivets comprise at least two separate rivet elements, and wherein at least one of said rivet elements is at least partly made of a memory material. The memory material here has at least a first memory transfer temperature, wherein the rivets can be disassembled by heating the article, the rivets and/or the rivet elements. The rivets are preferably heated. More preferably, the rivets are heated to a temperature within the range of this first memory transfer temperature. This allows exceptionally easy disassembly of rivets on the textile article, whereby a large number of rivets can be disassembled at the same time. This eliminates the need for manual removal of rivets and the disassembly process can be automated in its entirety.

According to some embodiments, the deformable rivet element is made entirely of the memory material.

Preferably, the textile article is assembled by heating the article, rivets, and/or rivet elements to a temperature within the range of the first memory transfer temperature. The composition of the article within this temperature range, 'programs' the rivets of the textile article in their permanent, closed form. According to an embodiment, the first memory transfer temperature is comprised between 100 and 200°C. If a thermostimulus with a temperature range below 60°C could cause a form change in the rivet, the integrity of the assembled textile articles could be compromised in everyday situations where the articles are exposed to temperature increases, such as in the washing machine or dryer. On the other hand, the temperature range of the one or more thermostimuli should be below the melting temperature of the rivet as well as of its individual parts. Since synthetic textile materials may melt at temperatures higher than 200°C, whereby they are lost or can cause undesired contamination of the other materials, the said upper limit is chosen. Preferably, the first memory transfer temperature is comprised between 100 and 200°C, more preferably between 100 and 160°C. Some textile products, such as cotton, already degrade when exposed to temperatures of 180°C and above with prolonged exposure. In order to minimise the risk of degradation, an upper limit of 180°C, more preferably 160°C, even more preferably 140°C is preferably used.

An embodiment concerns the textile article obtained by a method according to the first aspect, or the textile article comprising one or more rivets according to the second aspect.

In what follows, the invention is described by way of non-limiting figures illustrating the invention, and which are not intended to and should not be interpreted as limiting the scope of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic cross-section of a rivet (1) according to an embodiment of the present invention in open (top) and closed (bottom) form. At the top, the open form of the rivet (1) is shown, wherein the rivet consists of two rivet elements (2,3). The rivet (1) shown in Fig. 1 comprises a rivet (3) consisting of a memory material, which can be arranged in a receiving element (2). This receiving element (2) is not made of a memory material and is preferably rigid. When inserting the rivet (3) into the receiving element (2), and when subsequently applying a mechanical force to the whole of the elements (2,3) by means of a device suitable for compressing rivets, the end (4) of the rivet (3) is deformed such that the rivet is closed as shown in the bottom of Fig. 1. During assembly, or compressing, of the rivet, a temperature is used between 100 and 140°C, preferably 120°C. The memory material is thus programmed in its temporary, closed form, as shown at the bottom of Fig. 1. The rivet retains its closed confirmation at room temperature, as well as at common usage temperatures. When reheating the rivet to a temperature between 100 and 140°C, preferably 120°C, the rivet spontaneously returns from its temporary, closed form (bottom) to its permanent, open form (top). This allows easy reuse of the rivet and considerably simplifies the recycling process of rivets on textile products, and these textile products themselves.

Figure 2A shows the perspective view of a rivet (1), in particular a button with open (2) (left) and closed button face (2) (right), according to an embodiment of the present invention. The rivet (1) comprises a rivet (3) made of a memory material, while the button face (2) or the receiving element (2) is made of a rigid non-memory material. The end (4) of the rivet (3) is capable of deformation under the influence of temperature stimuli and takes a temporary, closed form under the influence of elevated temperature and the application of a mechanical force. Upon reheating to its first memory transfer temperature, the end (4) of the rivet (3) returns to its permanent, open form and the rivet (1) spontaneously falls apart.

Figure 2B shows different decorative embodiments of a button face. These button faces are not made of a memory material, so that they would not lose their decorative design when reused.

Figure 3 shows a perspective view of a rivet, in particular of the various rivet elements of a press stud, according to an embodiment of the present invention. The press stud essentially comprises two rivets (A,B), each of which is attached to two separate textile parts, to be connected by the press stud. A press stud as shown in Fig. 3, for example, is commonly used as a closure on a denim jacket. There is an externally visible rivet (A) and an invisible rivet (B) when the press stud is closed. The rivet elements (2) are made of a rigid material, while the rivet elements (3) comprise a memory material. In particular, the deformation points (5) are deformed when assembling the rivets (A, B) so that the rivets can be assembled in their temporary, closed form. Equivalent to the previous figures, the assembly of the rivets is done by applying a temperature stimulus and mechanical force, while the rivets spontaneously come apart when the temperature is increased again to the first memory transfer temperature of the memory material.

Figure 4 shows a perspective view of a rivet, in particular of the various rivet elements (2,3) of a ring opening or 'eyelet', according to an embodiment of the present invention. In this case, the ring (6) to be deformed is in particular carried out as a memory material, the transition between permanent and temporary forms being triggered by means of a temperature change. Figure 5 shows a possible heating unit (8) for use in the disassembly process described, where the disassembly process is a continuous process for smaller textile articles such as clothing and accessories. In a preferred form, the heating unit (8) will consist of two sections, namely a heating section and a cooling section (not shown in Figure 5). In the heating section of the heating unit (8) a turbulent air flow is obtained by means of a tumble function (13) of the device. The textile article is supplied by means of a conveyor belt (9) that runs through the device. The articles are heated intensely and homogeneously by means of heating elements (10) such as heat resistors, infrared heating, or other indirect heat sources. The forced heat convection is further increased due to the moist air flow, i.e. hot and pressurised steam via steam generators (11). A collection system (12) for produced moisture such as water can be provided at the bottom of the device. In a maximum of 5 minutes (preferably less than 3 minutes) the textile product will pass through the steam oven at temperatures of 180 to 200°C. The rivets of the textile product will change from their temporary, closed form to their permanent, open form, whereby the various product components fall apart (manually or automatically, for example by means of the tumble device).

Figure 6 respectively shows the temperature curve, the deformation and the tension on a rivet during multiple assembling and dismounting over a time course of 140 minutes. After heating to 120°C and applying mechanical deformation at 0 minutes, the rivet is in the assembled state in about 30 minutes. The rivet retains its closed form until reheated to 120°C and proceeds to the disassembled state in approximately 60 minutes. The process of assembly and disassembly is repeated from 60 to 120 minutes. From the graphs of Fig. 6, it becomes apparent that the rivet successfully transitions between its open and closed configuration several times upon repeated heating to the first memory transfer temperature.